Frog Prince is a failed attempt of wizard student Bart to cast the frog-to-prince spell.
The Simpsons Tapped Out
Frog Prince is a character in the game. You can buy him for 25 donuts during the Treehouse of Horrow XXV sale. He is available to buy until November 12, 2014. If you tap him in game he will puke and sometimes say a random message.